<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    .zhijiao, .dengyao {
        width: 100px;
        height: 0;
        /*background-color: #bfa;*/

    }
    .zhijiao {
        border-bottom: 100px solid red;
        border-right : 40px solid transparent;
    }
    .dengyao {
        border-bottom: 100px solid black;
        border-right : 40px solid transparent;
        border-left : 40px solid transparent;
    }
</style>
<body>
<div class="zhijiao"></div>
<div class="dengyao"></div>

</body>
</html>
